Concentration process for flotable substances as ores, coals, graphite, and the like



Patented Jan. 6, 1931 UNITED STATES PATENT-OFFICE j WILHE'LM seamen, or IBOCHUML, GERMANY CONCENTRATION PROCESS FOR FLOTABLE SUBSTANCES AS ORES, COALS, GRAPHITE, AND THE LIKE No Drawing. Application filed April 25, 1928, Serial Na. 272,861, and in Germany May 4, 1927.

The invention relates to the treatment of ore, coal, graphite and the like, where the collective affinity of oils and similar substances is utilized to make a separation, especially to the so called flotation process, in which the substances adhering to the oil are separated from the rest of the pulp by the use of a gas (such as air) in form of a froth. In these processes it is known to influence the flota- 1o tive qualities by the use of reagents in addition to the oils. The known reagents are in numerous cases ineffective or give unsatisfactory results with regard to concentration or recovery or both; this is invariably thexcase with ores which are refractory to flotation on account of geologic or atmospherical influence.

It has been found that the flotability can be influenced, specially also in the last mentioned difficult examples, by the addition of reagents which contain bodies which are derived from the polythionic acids. The poly thionic acids are chemically defined as acids of the type H S O where amay vary from 2 to 6. The simplest bodies in question are the salts of these acids, the thionates, neutral or acids. Of these salts, those of the polyvalentmetals are generally speaking more effective than those of the monovalent metals. The invention contemplates the use of stable metal salts of the-polythionic acids, which term designates the polythionates which are stable under flotation conditions. The addition of these reagents can be made,

either before, or during or after finecgrinding. They can be added alone or in combination with the addition of flotation oils or other reagents, the substances being added either simultaneously or in succession. The froth may be produced in any known'way as by beating air into the pulp by mechanically driven agitators or' introducing the air under pressure. In numerous cases it has been found that the action of the reagents of the invention can be enhanced by the use of additional reagents which yield or produce hydrogen or hydroxyl ions. The flotability can thus be influenced orimproved by the additional use of reagents such as acid or acid Sub$t lll('0 or bases or basic substances. The

combination to be employed in each specific case is dependent on the character of the ore to be treated. Generally speaking the former combination has shown good results in treating lead, copper and .silver minerals, while the latter combination shows good results in treating zinc, antimony arsenic ores and also pyrites.

It has further been found, that the addition of the reagents of this invention enables the selective or differential flotation of certain constituents or groups of such. In differential flotation it is of importance to increase the difference of the flotative qualities of two or more constituents and for this purpose the reagents of the invention are very well suited. It is thus possible to recover first one substance or a group of substances, leaving the other in the pulp, which can be partially or totally recovered by a subsequent treatment. For this differential separation the order of application of additional reagents and their character is of importance. It has been already distinguished between substances which have their flotative qualities enhanced by use of basic reagents as additional reagents, which hereinafter are called substances of the first class, and substances, for which the additional use of acid reagent is appropriate, which hereinafter are called substances of the second class.

In numerous cases in which ores have been treated containing substances of the first class, it was found to be the most effective way of treatment torecover these substances by employing, apart from the reagents of the invention, hydroxyl ions in form of additional reagents, and to recover the substances left in the pulp by the subsequent addition of acid reagents. If different substances of the second class are present it has been noted' that thesepa-ration is more or less dependent on a higher or lower hydrogen ion concentration in the pulp. It is therefore possible also by gradually increasing the addition of acid reagents to separate several substances of the second class.- If substances of the first class are entirely absent, it is suitable to adopt the latter method only, that is, apart from the addition of the reagents of the invention, to

add as additional reagents such having an acid character, if necessary in a gradually increasing amount.

Ewamples 1. A pulp, of 500 g. of finely ground leadsilver ore, containing 2.9% Pb and 290 g. Ag per metric ton, was for ten minutes agitated with 4 ccm. of a 5% iron-dithionate solution. Then 1 g. of waterglass and some drops of a hardwood-tar oil were added. gave 20 g. lead concentrate with 60.5% Pb and 6.2 kg. Ag per metric ton, corresponding to a recovery of 83% of the lead and 85% of the silver. A parallel test, made in exactly the same manner, but without the addition of the thionate gave only a concentration of 52% Pb and 5.3 kg. Ag with recovery of 73% of'the lead and 74% of the silver.

2. 1000 kg. of a zinc ore, containing 8.2% Zn, were ground wet under the addition of 1000 ccm. of a 20% zinc trithionate solution; before flotation 500 gsulfuric acid in a 1: 1 dilution were added and the flotation carried out in a pulp densitv of 1 :4 under the addition of 250 g. of a 1 :1 mixture of phenol and hardwood-tar oil. 151 kg. zinc concentrate with 51% Zn were obtained, corresponding to a recover of 93% of theZn. A parallel test made with 250 kg. of the same ore under the same condition but without the addition of the thionate gave 37.'7 kg. zinc concentrate with48.3% Zn equal to a recovery of 89% of the zinc.

3. 500 g. of lead zinc slimes of a wet mechanical mill, containing 5.2% Pb and 8.0% Zn, were treated for 10'n1inutes with 2.5 ccm. of a. 10% mixture of several zincpoly-thionates, chiefly triand tetrathionates, and then ,.floatednnder the addition of 0.5 g. waterglass and several drops of creosote oil. A lead concentrate was first obtained. Then 2 com. of a concentrated solution of Cu S0 1 ccm. of a. 1: 1 solution of H SO and some drops of a birch tar oil, were added and a zinc concentrate was floated. The results of this test are shown in the following table:

4. 400 g. of a finely ground copper pyrite- I iron pyrite ore with 2.5% Cu and 23.5% Fe were treated in a 1:4 pulp with 2 ccm. of a 10% sodiumtetrathionate solution for five minutes, and then under the addition of 1 g. of soda ash and several drops of an acetone oil a copper product floated. Then 2gH SO, in 1:1 dilution and several drops of a mixture ofcresol and wood-tar oil (1: 1) were The flotation added and a pyrite concentrate obtained. The copper concentrate contained 20.5% Cu and 26.2% Fe, with a copper recovery of 73.3%. The pyrite product assayed 1.5 Cu and 41.0% Fe, corresponding to a pyrite recovery of 90%. The tailings carried only 0.05% Cu and 7.5% Fe, of which about 5% were present in form of ironsilicate.

5. Of a stibnitc ore, containing arsenical pyrite with 7.2% Sb and 0.5 As, 500 g. were ground with 2000 ccm. water and .4 ccm. of a 10% manganese and irondithionate mixture, then agitated with 2.5 ccm. concentrated CuSO. and 1 com. of a 1:1 H SO solution and then under the addition of woodtar oil subjected to flotation, a concentrate containing 49% Sb and 1.2% As was'first floated, equal to an antimony recovery of 86%. Then after the addition of 3 ccm. H SO. (diluted 1: 1) 40% of the arsenic contents were obtained in form of a second concentrate. The tailings'assayed 0.7% Sb and 0.2% As.

From'these examples it will be seen that pure thionates and also mixtures of such can be employed, and not only mixtures of polythionates of one metal but also of diflerent metals, generally speaking thionate contain ing reagents can be emplo ed. The quantities employed vary according to the character of the substances to be treated and generally vary between 0.05-1 kg. per metric ton treated. I

Having thus described my invention what Iclaim to protect is:

1. The step in the froth flotation process of treating finely divided metaliferous sulphide ores to effect a separation of the sulphide minerals, which comprises treating the ores with a flotation solution containing a stable metal salt of theipolythionic acids oi" the formula H S O 2. The ste in the froth flotation process of treating nely divided metaliferous sulphide ores to effect a separation of the sulphide minerals, which comprises treating the ores with a flotation solution containing a stable polyvalent salt of the polythionic acids of the formula H SXO 3. The step in the froth flotation process of treating finely divided metaliferous sulphide ores to efiect a separation of the sulphide minerals, which comprises treating the ores with a flotation solution containing a stable metal salt of the polythionic acids of the formula H .S,.O and substances containing 11 droxyl ions.

4. e step in the froth flotation process of treating finely divided metaliferous sulphide ores to effect a separation of the sulphide minerals which comprises treating the ores with a flotation solution containing a stable polyvalent metal salt of the polythionic acids of the formula H S O and substances containing hydroxyl ions.

5. The frothflotation process of treating finely divided metaliferous sul hide ores to eifect a separation of the sulphi e minerals,

" which comprises subjecting the ores to flotation treatment in the presence of a solution containing a stable metal salt of the polythionic acids of the formula H S O and a substance having hydroxyl ions whereby the sulphides to be separated from the ore are prevented from adhering to the froth, and

thereafter adding to the solution a substance ore are prevented'from adhering to the froth,

and thereafter adding to the'solutiona substance having hydrogen ions whereby the flotation of the sulphides, which were prevented from flotation in the first instance, is permitted.

7. The froth flotation process. of treating finely divided metaliferous sulphide ores to effect a separation of the sulphide minerals which comprises subjecting the ores to flotation treatment in the presence of a solution containing at least two different stable metal salts of the polythionic acids of the formula I-LS O and a substance having hydroxyl ions whereby the sulphides to be separated from the ore are preventedfrom adhering to the froth, and thereafter adding to the solution a substance having hydrogen ionswhereby the flotation of the sul hides, which were prevented from flotation 1n the first instance, is permitted. a

8. The froth flotation process of treating finely divided metaliferous sulphide ores to effect a separation of the sulphide minerals, which comprises subjecting the ores to flotation treatment in the presence of a solution containing at least an alkali salt and a stable polyvalent salt of the polythionic acids of the formula H S O and a substance having hydroxyl ions whereby the sulphides to be separated from the ore are prevented from adhering to the froth, and thereafter adding to the solution a substance having hydro en ions whereby the flotation of the sulphi es, which were prevented from flotation in the first instance, is permitted.

WILHELM soHAFER. 

